1. Field of the Invention
This invention relates to pipe swivel joints, and more particularly, to such swivel joints for use in both normal and relatively high temperature environments.
2. Description of the Prior Art
Pipe swivel joints are commonly used by the oil and gas industry for interconnecting lengths of metal pipes to form an articulated flow conduit between two locations. Such swivel joints commonly have a generally annular inner body member having a bore extending axially therethrough and an annular outer body member surrounding the inner body member. The inner and outer body members are rotatably interconnected by a plurality of ball bearings and one or more annular sealing members mounted at a junction of the inner and outer members prevent leakage of fluid from the swivel joint. Swivel joints used at moderate temperatures commonly use annular resilient sealing members while metal seals are used at higher temperatures. Such metallic seals usually permit more leakage of fluids than do the resilient seals if used at lower temperatures. For this reason when the normal operating temperature is relatively low resilient seals are commonly used. However, in the petroleum industry there is sometimes the danger of a fire either inside the piping itself or outside the piping system in the vicinity of the swivel joint. When fire causes the joint temperature to rise to higher levels, the resilient seal of the swivel joint can deteriorate or be destroyed so that it will no longer be effective as a seal.
Some of the swivel joints use a resilient seal and a metal anti-extrusion ring at the junction of the inner and outer body members to prevent the resilient seal from being extruded into the area between the inner and outer body members. However, if the resilient seal should be destroyed the anti-extrusion ring may move away from the junction of the body members and the swivel joint may have excessive fluid leakage.